• S. De Santis, J.M. Byrd
  LBNL, Berkeley, California
• M.G. Billing, J.P. Sikora
  CLASSE, Ithaca, New York

Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

We report on the optimization of TE Wave measurements at the Cesr-TA ring at Cornell University. The CESR storage ring is currently used as a testbed for technologies to be used in the damping rings of the International Linear Collider. The TE Wave measurement method utilizes capacitive buttons (BPMs) in the ring to excite and detect a propagating electromagnetic wave corresponding to the beampipe's fundamental TE mode. The presence of low-energy electrons along the wave path changes its propagation characteristics, which can be detected by analyzing the received signal. By choosing the machine fill pattern (gaps and bunch trains length) it is possible to modulate the density of the electron cloud and derive information on its rise and fall times by observing the detected signal spectrum. The possibility of circulating both electron and positron beams in the ring enabled us to separate the contribution of primary photoelectrons, which are independent on the circulating particle nature, from the transverse resonant mechanism, which can increase the primary electron density many times over and which only takes place with a circulating positron beam.

• Y. Li, M.G. Billing, S. Greenwald, T.I. O'Connell, M.A. Palmer, J.P. Sikora, E.N. Smith, K.W. Smolenski
  CLASSE, Ithaca, New York
• J.N. Corlett, R. Kraft, D.V. Munson, D.W. Plate, A.W. Rawlins
  LBNL, Berkeley, California
• K. Kanazawa, Y. Suetsugu
  KEK, Ibaraki
• M.T.F. Pivi
  SLAC, Menlo Park, California

Funding: Work supported by the National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program

Wiggler magnets are one of the key components in the ILC Damping Ring. It is critical to the ILCDR GDE to understand electron cloud (EC) growth and patterns, and to develop EC suppression techniques in the wiggler beampipes. The CESR-c superconducting wigglers, closely matching the parameters of the ILCDR wigglers, serve as unique testing vehicles. As part of the CesrTA project, we replaced the copper beampipes of two SCWs with EC diagnostic beampipes, where one of the beampipes is uncoated and the second is coated with a thin TiN film. Each of the EC diagnostic beampipes is equipped with three retarding field analyzers (RFAs) at strategic longitudinal locations in the wiggler field. Each of the RFAs has 12-fold segmentation to measure the horizontal EC density distribution. To maintain sufficient vertical beam aperture and to fit within the SCW warm bore, a thin style of RFA (with a thickness of 2.5 mm) has been developed and deployed. These SCWs with RFA-equipped beampipe have been installed and successfully operated in the re-configured CesrTA vacuum system. This paper describes the design and the construction of the RFA-equipped SCW beampipes and operational experience.

• M.A. Palmer, M.G. Billing, J.R. Calvey, G.W. Codner, S. Greenwald, Y. Li, X. Liu, J.A. Livezey, R.E. Meller, R.M. Schwartz, J.P. Sikora, C.R. Strohman, W.S. Whitney, T. Wilksen
  CLASSE, Ithaca, New York

Funding: Support provided by the US National Science Foundation and the US Department of Energy.

A central component of the operation of the Cornell Electron Storage Ring as a Test Accelerator (CesrTA) for ILC Damping Rings R&D is the characterization of electron cloud growth in each of the principal vacuum chamber types in use in the storage ring. In order to facilitate measurements in chambers with tightly constrained external apertures, retarding field analyzers have been developed that can be deployed in regions with as little as 3mm of available aperture. We report on the design, fabrication, characterization and operation of devices that are presently deployed in CESR drift, dipole, and wiggler chambers.

• M.A. Palmer, J.P. Alexander, M.G. Billing, J.R. Calvey, S.S. Chapman, G.W. Codner, C.J. Conolly, J.A. Crittenden, J. Dobbins, G. Dugan, E. Fontes, M.J. Forster, R.E. Gallagher, S.W. Gray, S. Greenwald, D.L. Hartill, W.H. Hopkins, J. Kandaswamy, D.L. Kreinick, Y. Li, X. Liu, J.A. Livezey, A. Lyndaker, V. Medjidzade, R.E. Meller, S.B. Peck, D.P. Peterson, M.C. Rendina, P. Revesz, D.H. Rice, N.T. Rider, D. L. Rubin, D. Sagan, J.J. Savino, R.D. Seeley, J.W. Sexton, J.P. Shanks, J.P. Sikora, K.W. Smolenski, C.R. Strohman, A.B. Temnykh, M. Tigner, S. Vishniakou, W.S. Whitney, T. Wilksen, H.A. Williams
  CLASSE, Ithaca, New York
• J.M. Byrd, C.M. Celata, J.N. Corlett, S. De Santis, M.A. Furman, A. Jackson, R. Kraft, D.V. Munson, G. Penn, D.W. Plate, A.W. Rawlins, M. Venturini, M.S. Zisman
  LBNL, Berkeley, California
• J.W. Flanagan, P. Jain, K. Kanazawa, K. Ohmi, H. Sakai, K. Shibata, Y. Suetsugu
  KEK, Ibaraki
• K.C. Harkay
  ANL, Argonne
• Y. He, M.C. Ross, C.-Y. Tan, R.M. Zwaska
  Fermilab, Batavia
• R. Holtzapple
  CalPoly, San Luis Obispo, CA
• J.K. Jones
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• D. Kharakh, M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California
• E.N. Smith
  Cornell University, Ithaca, New York
• A. Wolski
  Cockcroft Institute, Warrington, Cheshire

Funding: Support provided by the US National Science Foundation, the US Department of Energy, and the Japan/US Cooperation Program.

In March of 2008, the Cornell Electron Storage Ring (CESR) concluded twenty eight years of colliding beam operations for the CLEO high energy physics experiment. We have reconfigured CESR as an ultra low emittance damping ring for use as a test accelerator (CesrTA) for International Linear Collider (ILC) damping ring R&D. The primary goals of the CesrTA program are to achieve a beam emittance approaching that of the ILC Damping Rings with a positron beam, to investigate the interaction of the electron cloud with both low emittance positron and electron beams, to explore methods to suppress the electron cloud, and to develop suitable advanced instrumentation required for these experimental studies (in particular a fast x-ray beam size monitor capable of single pass measurements of individual bunches). We report on progress with the CESR conversion activities, the status and schedule for the experimental program, and the first experimental results that have been obtained.

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